Method for producing carbon nanotubes and apparatus for producing carbon nanotubes

Abstract

The application discloses a carbon nanotube preparation method and a carbon nanotube preparation device. The carbon nanotube preparation method comprises the following steps: passing carrier gas: the carrier gas is passed into a growth bin; passing reactants: when the carrier gas is passed, the carbon source and the catalyst are passed into the growth bin to generate the carbon nanotube; and preheating the carrier gas: before the carrier gas is passed, at least part of the carrier gas is heated to keep the temperature of the central region of the growth bin at a preset temperature after the carrier gas is passed, so as to match the growth temperature of the carbon nanotube. The carrier gas preheated as the main heat source is directly supplied to the center of the growth bin, the heat efficiency is high, the energy consumption is low, the carbon deposition and shutdown are reduced; and the reactants are uniformly introduced into the center and fully mixed with the carrier gas, the temperature field is uniform, the radial temperature difference is small, the quality and yield of the carbon nanotube are improved, and the high-quality and low-cost large-scale preparation is realized.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube preparation technology, and particularly to a method for preparing carbon nanotubes, as well as a carbon nanotube preparation apparatus for performing the method. Background Technology

[0002] Carbon nanotubes, as nanomaterials with excellent mechanical, electrical, and thermal properties, have shown broad application prospects in new energy, electronic information, and composite materials. Their large-scale preparation technology has always been a research hotspot in materials science. Currently, chemical vapor deposition (CVD) is commonly used to prepare carbon nanotubes. Depending on the catalyst type, carbon source characteristics, and target carbon nanotube diameter, gaseous carbon sources such as methane, ethylene, propylene, and carbon monoxide are introduced into a closed growth chamber along with catalysts such as iron, nickel and their alloys, or organometallic compounds such as ferrocene and cobalt dicene. Then, the carbon source undergoes chemical reactions such as cracking and dehydrogenation on the catalyst surface, and carbon atoms are gradually deposited and oriented along the catalyst crystal structure, eventually growing into carbon nanotubes. In this process, the uniformity of the temperature field and the accuracy of temperature control within the growth chamber are the core factors that determine the quality of carbon nanotubes. For example, excessive radial temperature difference can lead to local agglomeration of the catalyst, uneven growth rate of carbon nanotubes, or even entanglement, which seriously affects the uniformity of tube diameter, purity, and yield of the product. In the preparation process, the temperature usually needs to be stabilized within ±5℃ of the target temperature. If the temperature fluctuation is too large, it may cause premature pyrolysis and coking of the carbon source or deactivation of the catalyst, reducing the utilization rate of raw materials.

[0003] In related technologies, chemical vapor deposition (CVD) preparation equipment generally adopts an external heating method, which heats the furnace wall by heating tubes wrapped around the outside of the growth chamber, and then uses the heat conduction and heat radiation of the furnace wall to transfer heat to the carrier gas, carbon source and catalyst inside the furnace, so that the temperature inside the furnace rises to the temperature required for carbon nanotube growth.

[0004] However, the furnace wall has strong thermal inertia and significant temperature regulation lag. The response time for heating or cooling typically takes several minutes to tens of minutes, making it difficult to adapt to dynamic process adjustments. In practical applications, when the inner diameter of the growth chamber is large, the heat conduction and radiation efficiency of the furnace wall decreases sharply. Multiple experiments have shown that when the inner diameter of the furnace tube exceeds 150mm, the radial temperature difference often exceeds ±5℃, failing to meet the requirements for high-quality carbon nanotube growth. Furthermore, the furnace wall being at a high temperature close to or exceeding the carbon nanotube growth temperature for extended periods easily leads to non-catalytic pyrolysis and deposition of reactants, especially the carbon source, on the furnace wall surface, forming a carbon deposit layer. This not only wastes raw materials and contaminates products but also disrupts the stability of the furnace temperature field due to the insulating effect of the carbon deposit layer, increasing the frequency of shutdowns for cleaning. For example, a shutdown for cleaning is required every 50-100 hours of operation, severely restricting the continuity and economy of production. In addition, external heating walls result in significant energy loss; the heat dissipation and radiation from the high-temperature furnace wall lead to substantial energy waste, with a thermal efficiency typically below 50%, significantly increasing production energy costs.

[0005] To address the aforementioned issues, how to optimize the temperature field distribution within the growth chamber through innovative heating mechanisms, improve the adaptability of large-diameter growth chambers, and reduce energy consumption and carbon buildup have become pressing technical challenges that need to be solved to promote the increase in carbon nanotube production capacity. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for preparing carbon nanotubes, using a pre-treated heated carrier gas as the main heat source, directly supplying it to the center of the growth chamber. This method has high thermal efficiency, low energy consumption, and reduces carbon buildup and downtime. Furthermore, the reactants are uniformly incorporated into the center and thoroughly mixed with the carrier gas, resulting in a uniform temperature field and small radial temperature difference. The mixing and heat distribution are optimized through vortex injection and parameter control, thereby improving the quality and yield of carbon nanotubes and achieving high-quality, low-cost, large-scale preparation.

[0007] The present invention also proposes a carbon nanotube preparation apparatus for performing the above-described carbon nanotube preparation method.

[0008] The carbon nanotube preparation method according to the present invention includes the following steps: Carrier gas is introduced into the growth chamber; Reactant flow: During carrier gas flow, carbon source and catalyst are introduced into the growth chamber to generate carbon nanotubes; Pretreatment of carrier gas: Before the carrier gas is introduced, at least a portion of the carrier gas is heated to drive the temperature of the central region of the growth chamber to remain at a preset temperature after the carrier gas is introduced, in order to match the growth temperature of carbon nanotubes.

[0009] The carbon nanotube preparation method according to the present invention has at least the following beneficial effects: By pretreating and heating at least a portion of the carrier gas before introducing the carrier gas, and simultaneously introducing a carbon source and catalyst into the growth chamber during the introduction of the carrier gas, the heated high-temperature carrier gas becomes the main heat source for maintaining the temperature of the central region of the growth chamber, thereby matching the growth temperature of the carbon nanotubes. This concept fundamentally changes the traditional heat transfer mode that relies on indirect heating from the furnace wall, transforming the carrier gas from a simple transport and dilution medium into an active heat source with efficient heat transport function. On the one hand, the carrier gas itself carries sufficient heat energy to act directly on the central region of the growth chamber through convection, significantly shortening the heat transfer path and reducing thermal resistance, thereby greatly improving heat utilization efficiency and reducing energy consumption. On the other hand, since the heated high-temperature carrier gas is concentrated in the central reaction zone, the reactants also converge with the carrier gas in this region, jointly forming... A dynamic thermal and concentration field centered on the core significantly reduces the probability of reactants contacting the high-temperature furnace wall, effectively suppressing non-catalytic pyrolysis and carbon deposition, extending continuous equipment operation time, reducing downtime for cleaning, and lowering maintenance costs and production interruption risks. Simultaneously, using pre-treated heated carrier gas as the primary heat source allows for precise setting and stable maintenance of the temperature in the central region of the growth chamber within the optimal temperature window for carbon nanotube growth. Optional low-power insulation measures around the growth chamber can offset minor heat loss, achieving high-precision, high-stability temperature control. This prevents catalyst deactivation, uneven carbon nanotube nucleation, or structural defects caused by temperature fluctuations or excessive radial temperature differences, ensuring uniform tube diameter, high purity, and good crystallinity of the product. This provides a robust thermal environment guarantee for the large-scale, low-cost, and stable production of carbon nanotubes.

[0010] According to some embodiments of the present invention, in the carbon nanotube preparation method, the carrier gas is introduced linearly and / or swirlingly into the central region of the growth chamber.

[0011] According to some embodiments of the present invention, in the carbon nanotube preparation method, the carbon source and the catalyst are introduced into the central region of the growth chamber through at least one pair of reactant channels uniformly arranged around the growth chamber.

[0012] According to some embodiments of the present invention, in the carbon nanotube preparation method, both reactant channels are arranged at an angle relative to the axis of the growth chamber; in the reaction, the carbon source, the catalyst, and the carrier gas all intersect at the axis of the growth chamber.

[0013] According to some embodiments of the present invention, in the carbon nanotube preparation method, at least a portion of the carrier gas flows along a spiral structure and is heated in the pretreatment carrier gas.

[0014] According to some embodiments of the present invention, in the carbon nanotube preparation method, at least a portion of the wall of the spiral structure is configured as an electromagnetic induction body. An alternating magnetic field is generated by an electromagnetic induction coil, which drives the electromagnetic induction body to heat up and heat the carrier gas flowing through the spiral structure.

[0015] According to some embodiments of the present invention, in the carbon nanotube preparation method, at least a portion of the carrier gas enters the growth chamber in a swirling direction during the passage of carrier gas.

[0016] According to some embodiments of the present invention, in the process of preparing carbon nanotubes, the flow rate and / or rotation intensity and / or centrifugal intensity of the carrier gas entering the growth chamber are adjusted to control the mixing uniformity of the carrier gas, the carbon source and the catalyst in the growth chamber, and / or control the radial temperature difference of the growth chamber.

[0017] The carbon nanotube preparation apparatus according to the present invention is used to perform the carbon nanotube preparation method according to the present invention, the carbon nanotube preparation apparatus comprising: Growth chamber; A heater capable of heating the carrier gas, the heater including a carrier gas main pipe, the central axis of the carrier gas main pipe coinciding with the central axis of the growth chamber, so as to drive the carrier gas axially into the central region of the growth chamber; At least one pair of reactant channels are uniformly arranged around the outer periphery of the main carrier gas channel. The reactant channels are inclined toward the central region of the growth chamber to drive the carbon source and catalyst to the central region of the growth chamber and mix with the carrier gas to generate carbon nanotubes.

[0018] The carbon nanotube preparation apparatus according to the present invention has at least the following beneficial effects: by aligning the central axis of the carrier gas main pipe of the heater with the central axis of the growth chamber, the carrier gas is axially introduced into the central region of the growth chamber. This coaxial arrangement ensures that the heat of the carrier gas directly acts on the core reaction region, avoiding heat loss and temperature unevenness caused by deflection. At the same time, at least one pair of reactant pipes inclined towards the central region are uniformly arranged around the outer periphery of the carrier gas main pipe, so that the carbon source and catalyst naturally flow into the high-temperature central region where the main carrier gas flows, forming a spatial overlap of heat and mass. This not only improves the mixing efficiency of reactants and carrier gas, but also reduces their non-catalytic contact with the sidewalls, thereby reducing the risk of carbon deposition and ensuring that the high-temperature carrier gas, carbon source and catalyst react efficiently in the optimal position, providing reliable hardware support for the continuous production of high-quality carbon nanotubes.

[0019] According to the carbon nanotube fabrication apparatus of the present invention, the heater further includes a core and an electromagnetic induction coil. The core is arranged in the main gas tube and forms a first gas channel with the main gas tube. The first gas channel communicates with the growth chamber and inputs the carrier gas. At least a portion of the inner wall of the main gas tube and / or at least a portion of the outer wall of the core has a helical surface to form a helical structure in at least a portion of the first gas channel. At least a portion of the wall of the helical structure is an electromagnetic induction element. The electromagnetic induction coil is energized to generate an alternating magnetic field and drive the electromagnetic induction element to heat up, thereby heating the carrier gas flowing through the helical structure. A second gas channel is provided in the middle of the core. The second gas channel extends along the side facing the growth chamber and communicates with the growth chamber to input a portion of the carrier gas. The first carrier gas channel is further provided with a spiral structure at one end that is connected to the growth chamber, so as to drive the carrier gas to swirl into the growth chamber; and / or, the pitch of the spiral structure gradually decreases along the side facing the growth chamber.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic cross-sectional view of the carbon nanotube fabrication apparatus according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the left-hand structure of the carbon nanotube preparation apparatus according to an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of a carbon nanotube fabrication apparatus according to another embodiment of the present invention; Figure 4 This is a schematic cross-sectional view of a carbon nanotube fabrication apparatus according to another embodiment of the present invention; Figure 5 This is a schematic flowchart of a carbon nanotube preparation method applied to the carbon nanotube preparation apparatus in an embodiment of the present invention.

[0022] Explanation of icon numbers: Growth chamber 1; Insulation layer 10; Inlet 11; Outlet 12; Inner cavity 13; Heater 2; Carrier gas main pipe 21; First carrier gas channel 211; Core 22; Outlet end 210; Second carrier gas channel 220; Annular end cap 23; Helical structure 3; Electromagnetic induction coil 4; Carrier gas auxiliary pipe 5; Reactant conduit 6. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0027] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] Therefore, such as Figures 1 to 4The diagram shows the apparatus for preparing carbon nanotubes proposed in this invention. It includes a growth chamber 1 capable of receiving a carrier gas, a carbon source, and a catalyst, and a heater 2 connected to the growth chamber 1 and configured to heat at least a portion of the carrier gas introduced into the growth chamber 1. Specifically, the carrier gas, carbon source, and catalyst are used to generate carbon nanotubes, wherein the heated carrier gas is the primary source of heat for maintaining the temperature required for carbon nanotube growth within the growth chamber 1. The growth chamber 1 provides a growth space for the carbon nanotubes and has an inlet 11, an outlet 12, and an axially extending inner cavity 13 arranged between them. A heat insulation layer 10 is provided around the growth chamber 1; alternatively, a low-power heat insulation and heating device can be used to reduce heat dissipation within the growth chamber 1. In some applications, the outlet 12 of the growth chamber 1 can be connected to a receiving chamber. Optionally, the carrier gas can be an inert gas such as argon or nitrogen, or a reducing gas such as hydrogen, or a mixture of inert and reducing gases. The composition of the carrier gas is generally selected based on the production objectives and process. During the generation of carbon nanotubes, all the carrier gas can be introduced into growth chamber 1 as a high-temperature carrier gas, or only a portion of the carrier gas can be introduced into growth chamber 1 as a high-temperature carrier gas, while the remaining carrier gas, mixed with the reactants, can be introduced into growth chamber 1 at a low temperature, i.e., below the growth temperature of carbon nanotubes. Optionally, the carbon source and catalyst can be introduced into growth chamber 1 separately or pre-mixed. In addition, the reactants may include other materials. For example, to facilitate the dilution or transport of the carbon source, a certain amount of carrier gas can be added to the carbon source, and the mixture can be introduced into growth chamber 1. The carbon source is the source of carbon atoms that constitute the carbon nanotube framework. One or more gaseous carbon sources such as methane, ethylene, and propylene can be selected, as well as one or more liquid carbon sources such as methanol and benzene, or one or more solid carbon sources such as camphor and naphthalene. The catalyst is the key substance that guides the decomposition of the carbon source and promotes the nucleation and growth of carbon nanotubes. One or more solid catalysts such as ferrocene, cobalt dicene, and nickel dicene can be selected. Before being introduced into growth chamber 1, the non-gaseous carbon source and catalyst can be pre-gasified.

[0029] It should be noted that the heated high-temperature carrier gas directly enters the growth chamber 1, efficiently transferring heat to the reactants and the growth environment of the growth chamber 1 through convection heat transfer. This replaces the traditional static thermal field that relies on furnace wall conduction and radiation, forming a dynamic thermal field and fundamentally changing the heat transfer mode. The heat required to maintain the temperature for carbon nanotube growth in the growth chamber 1 is mainly provided by the introduced high-temperature carrier gas. This heat includes: the heat required to control the temperature in the growth chamber 1 and stabilize the environment in the growth chamber 1 within the target temperature range required for carbon nanotube growth. This includes the heat consumed to compensate for heat dissipation from the growth chamber 1 and to heat the low-temperature reactants, as well as the heat required for the carbon nanotube generation reactions such as the cracking of gaseous carbon sources and the endothermic reaction of carbon atom deposition into the tube. The main part of this heat is provided by the introduced high-temperature carrier gas through convection heat transfer. It should be further noted that other auxiliary methods can also be used to heat the growth chamber 1, such as allowing the growth chamber 1 to receive additional low-power heat preservation heating, but the heat contribution is lower than that of the high-temperature carrier gas. This not only significantly shortens the heat transfer path and reduces energy loss caused by heat dissipation and thermal radiation from the outer wall of growth chamber 1, but also significantly improves thermal efficiency by more than 70% in actual tests. This not only reduces production energy consumption, but also promotes convection and diffusion with low-temperature reactants due to the high average kinetic energy and fast motion speed of the molecules in the high-temperature carrier gas. This effectively weakens the radial temperature gradient in growth chamber 1, making it easier to control the radial temperature difference within ±3℃. This meets the stringent requirements of carbon nanotube growth for temperature field uniformity and avoids catalyst agglomeration, carbon nanotube entanglement, or purity reduction caused by excessive local temperature differences. Meanwhile, the high-temperature carrier gas acts directly on the growth area as a heat carrier, avoiding non-catalytic pyrolysis of reactants caused by long-term high temperature of the furnace wall, significantly reducing carbon buildup, extending continuous production time, and reducing downtime cleaning frequency and maintenance costs. In addition, since the heat of the high-temperature carrier gas is mainly controlled by the heater 2, and the temperature and flow rate adjustment of the high-temperature carrier gas responds faster, it solves the temperature lag problem of traditional external heating wall heating, providing a reliable thermal environment guarantee for the stable and efficient growth of carbon nanotubes, and taking into account both the capacity improvement needs of the large-diameter growth chamber 1 and the product quality control requirements.

[0030] like Figure 1As shown, in some embodiments of the present invention, the heater 2 is provided with a spiral structure 3 so that at least part of the carrier gas is heated in the spiral flow. Compared with a straight pipe channel, the spiral structure 3 can extend the heating stroke of the carrier gas, increase the contact time between the carrier gas and the heating surface within the same axial length, and improve the heating efficiency. At the same time, the spiral structure 3 induces the carrier gas to generate rotation and turbulence, which can effectively destroy the thermal boundary layer of the carrier gas, enhance the convective heat transfer process, avoid local overheating or underheating of the carrier gas, significantly optimize the uniformity of the carrier gas heating, and provide a more stable and more uniformly distributed heat source for the growth chamber 1, thereby helping to improve the uniformity of the temperature field in the growth chamber 1 and laying the foundation for the uniform growth of carbon nanotubes. In one embodiment, the pitch of the spiral structure 3 is a constant pitch structure; in another preferred embodiment, the pitch of the spiral structure 3 is a variable pitch structure, wherein the pitch can be gradually reduced from the air inlet to the air outlet direction. Under the induction of the gradually decreasing pitch, the gradually enhanced disturbance generated by the carrier gas further destroys the thermal boundary layer of the carrier gas, strengthens the convective heat transfer process, and improves the heating uniformity of the carrier gas.

[0031] Specifically, the heater 2 is equipped with an electromagnetic induction coil 4, and at least a portion of the wall of the spiral structure 3 serves as an electromagnetic induction element. When the electromagnetic induction coil 4 is energized, it generates an alternating magnetic field, which in turn causes the electromagnetic induction element to heat up, thereby heating the carrier gas flowing through the spiral structure 3. This method overcomes the drawbacks of traditional resistance heating wires or external heating walls, such as high thermal inertia and long heat transfer paths. It utilizes an alternating magnetic field to heat the electromagnetic induction element, directly heating the flowing carrier gas. The heating wall surface of the electromagnetic induction element is in direct contact with the carrier gas, resulting in more direct heat transfer and less heat loss. The electromagnetic induction coil 4 can be used as follows: Figure 1The coil 22, as shown, can be wound around the outside of the carrier gas main pipe 21, or placed flat on one side of the carrier gas main pipe 21, or arranged in other suitable positions, as long as the carrier gas main pipe 21 and / or the core 22, which act as the electromagnetic induction body, are partially or entirely located within the alternating magnetic field generated by the electromagnetic induction coil 4, resulting in efficient heating due to electromagnetic induction. In some applications, the temperature of the electromagnetic induction body can be quickly changed by adjusting the power of the induction coil, causing the temperature of the carrier gas to change rapidly and be introduced into the growth chamber 1. This enables precise and real-time control of the dynamic thermal field within the growth chamber 1, effectively solving the temperature lag problem of traditional heating methods and providing a more sensitive thermal environment guarantee for the stable and efficient growth of carbon nanotubes. Furthermore, the heater 2 is connected to one side of the growth chamber 1, and the pitch of the spiral structure 3 gradually decreases along the side facing the growth chamber 1 (not shown in the figure). This variable pitch design causes the carrier gas to generate progressively stronger disturbances as the pitch decreases when flowing in the spiral channel, further enhancing the turbulence intensity in the convective heat transfer process, more effectively destroying the thermal boundary layer, and improving the uniformity of heating of the carrier gas. Furthermore, the tapered pitch can further extend the effective heating path within the same axial length, improving heating efficiency and reducing energy loss without increasing the axial dimensions of the equipment. This ensures a more consistent temperature distribution of the carrier gas entering the growth chamber 1, which is beneficial for maintaining a stable temperature environment within the growth chamber 1. In other applications, the spiral structure 3 is located at the end of the first carrier gas channel 211 that connects to the growth chamber 1, to drive the carrier gas in a swirling direction into the growth chamber 1. Specifically, for example... Figure 1 As shown, an annular end cap 23 is detachably provided at the outlet end 210 of the carrier gas main pipe 21. The inner diameter of the air passage of the annular end cap 23 is smaller than the inner diameter of the carrier gas main pipe 21. The high-temperature carrier gas flowing out of the carrier gas main pipe 21 passes through this annular end cap 23 and forms a composite flow field with axial propulsion and circumferential rotation components, entering the growth chamber 1 in a swirling flow. (Refer to...) Figure 4 In another embodiment, the carrier gas main pipe 21 can be removed or omitted. Figure 1 The annular end cap 23 is incorporated, and the spiral structure 3 is extended forward to or near the outlet end 210 of the carrier gas main pipe 21. This design reduces the axial propulsion component of the carrier gas while increasing its circumferential rotational component when entering the growth chamber 1, allowing the carrier gas to flow into the central region of the growth chamber 1 in a swirling flow with a greater rotational component. As a result, the carrier gas enters the growth chamber 1 in a swirling flow, generating strong shear and centrifugal forces upon entry, further optimizing the radial uniformity of the temperature field within the growth chamber 1 and reducing radial temperature differences. Simultaneously, the swirling flow prolongs the residence time of the carrier gas within the growth chamber 1, increasing heat transfer and reaction duration, improving heat utilization and the sufficiency of the carbon nanotube growth reaction. Furthermore, the swirling flow enhances the mixing uniformity of the carrier gas, carbon source, and catalyst, reducing the probability of catalyst deactivation or agglomeration due to localized low temperatures, contributing to the acquisition of carbon nanotubes with uniform diameter and higher purity, and improving the effective utilization rate of raw materials and production efficiency.

[0032] Specifically, refer to Figure 1In some embodiments of the present invention, the heater 2 includes a main gas pipe 21 and a core 22. The core 22 is disposed in the main gas pipe 21 and forms a first gas channel 211 between the core 22 and the main gas pipe 21. The first gas channel 211 communicates with the growth chamber 1 and inputs the gas. At least a portion of the inner wall of the main gas pipe 21 and / or at least a portion of the outer wall of the core 22 has a helical surface to form a helical structure 3 in at least a portion of the first gas channel 211. This arrangement integrates the first gas channel 211 with the helical heating structure, so that the gas is helically heated as it flows through the channel between the main gas pipe 21 and the core 22, resulting in a compact structure and a short heat transfer path. In some specific embodiments, the outer diameter of the core 22 is substantially equal to the inner diameter of the main gas pipe 21, so that the helical structure 3 constitutes the entire first gas channel 211. Of course, in other embodiments, the outer diameter of the core 22 can be smaller than the inner diameter of the carrier gas main pipe 21. Optionally, a straight channel (not shown in the figure) is formed between the carrier gas main pipe 21 and the core 22. The straight channel and the spiral structure 3 together constitute the first carrier gas channel 211. Furthermore, the spiral surface is directly formed on the channel wall to ensure that the carrier gas is heated synchronously during transportation, avoiding heat loss caused by additional diversion or reversal heating. At the same time, the design of the first carrier gas channel 211 communicating with the growth chamber 1 ensures that the high-temperature carrier gas can smoothly enter the growth chamber 1, providing a stable channel for subsequent heat transfer and reaction, and improving the overall thermal efficiency and reliability of the device. Common electromagnetic inductors are made of conductive graphite, conductive ceramics, or conductive metal alloys. The carrier gas main pipe 21 and the core 22 may be made of the same or different materials. For example, the carrier gas main pipe 21 may be made of conductive graphite and the core 22 may be made of conductive graphite; another example is that the carrier gas main pipe 21 may be made of conductive graphite and the core 22 may be made of conductive ceramics or conductive metal alloys; yet another example is that the carrier gas main pipe 21 may be made of conductive ceramics and the core 22 may be made of conductive graphite or conductive metal alloys; and yet another example is that the carrier gas main pipe 21 may be made of conductive metal alloys and the core 22 may be made of conductive metal alloys. These materials possess excellent electrical conductivity, high thermal stability, and low thermal expansion coefficient. They not only maintain structural stability in electromagnetic induction heating or high-temperature environments, and are not prone to deformation or failure due to thermal stress, but also ensure significant eddy current heating effect under the action of electromagnetic induction coil 4 due to their good electrical conductivity, thereby improving the heating efficiency of the carrier gas. Furthermore, their high-temperature resistance allows them to withstand temperatures of 1000℃~1500℃ or even higher for extended periods. Isostatic graphite, molded graphite, silicon carbide ceramics, doped silicon nitride ceramics, niobium alloys, etc., which have excellent electrical conductivity, high thermal stability, and low thermal expansion coefficient, are all suitable as long as they meet the requirements of process temperature, thermal stability, physicochemical stability, and high thermal conversion efficiency, and can meet the high-temperature conditions required for carbon nanotube growth.Specifically, when the core 22 and the carrier gas main pipe 21 are made of the same material, the core 22 and the carrier gas main pipe 21 cooperate to form a first carrier gas channel 211 that is stable in terms of heat and heating. Under the action of electromagnetic induction and synergistic heating, the carrier gas is uniformly and continuously heated, ensuring the temperature of the high-temperature carrier gas entering the growth chamber 1 is stable, which helps to maintain the uniformity of the temperature field inside the growth chamber 1.

[0033] Refer to Figure 3 In some embodiments of the present invention, a second carrier gas channel 220 is provided in the middle of the core 22. The second carrier gas channel 220 extends along the side facing the growth chamber 1 and communicates with the growth chamber 1 to input a portion of the carrier gas. On the one hand, since the core 22 is made of a conductive and high-temperature resistant material, it can also serve as a heating element, allowing a portion of the carrier gas to be directly heated inside the core 22, increasing the path and method of carrier gas heating, and improving the flexibility and uniformity of carrier gas heating; the carrier gas introduced into the growth chamber 1 through the second carrier gas channel 220 can also be heated by the core 22, and can even be heated into high-temperature carrier gas and introduced into the radial central region of the growth chamber 1. Secondly, a further option is that the inner wall of the second carrier gas channel 220 can also be set as a spiral channel, allowing at least a portion of the carrier gas flowing through it to rotate and flow into the radial central region of the growth chamber 1. On the other hand, the carrier gas in the second carrier gas channel 220 can cool the central area inside the core 22 after heating, avoiding the risk of thermal stress concentration or explosion caused by local overheating of the core 22, improving the safety and durability of the device operation, and ensuring that the carrier gas output from the second carrier gas channel 220 is at a suitable temperature, so that it will not cause premature catalyst deactivation or carbon source coking when participating in the reaction in the growth chamber 1.

[0034] Refer to Figures 1 to 3 As shown, in some embodiments of the present invention, at least one pair of uniformly arranged reactant pipes 6 are provided around the outer periphery of the carrier gas main pipe 21. The reactant pipes 6 are used to introduce carbon sources and catalysts into the growth chamber 1. This symmetrical and uniformly distributed design allows reactants to be injected into the radial central region of the growth chamber 1 from multiple directions at a certain angle, avoiding excessively high or low local concentrations caused by unilateral feeding, and promoting the formation of a uniform concentration field of reactants in the center of the growth chamber 1. It is readily understood that the number of reactant pipes 6 is even and they are arranged in pairs. The reactant pipes 6 are uniformly distributed circumferentially around the carrier gas main pipe 21; furthermore, the central axes of all reactant pipes 6 are inclined and intersect at point O, and each pair of reactant pipes 6 is symmetrically arranged around point O. (Refer to...) Figure 1Point O is located in the radial center region of growth chamber 1, or more specifically, on the central axis AA of growth chamber 1. This arrangement of the reactant conduit 6 firstly allows reactants to be injected symmetrically from multiple angles in three-dimensional space into the radial center region of growth chamber 1, avoiding excessively high or low local concentrations due to asymmetrical feeding, thus laying the foundation for a uniform concentration field. Secondly, it causes reactants entering from different directions to collide at point O, mutually restraining each other and converging in the radial center region of growth chamber 1, where they merge with the high-temperature carrier gas also converging there. Furthermore, the collision of reactants at point O induces strong turbulence and shearing effects, which is beneficial for the uniform mixing of carbon source, catalyst, and carbon source, laying a crucial foundation for the uniform nucleation and synchronous growth of carbon nanotubes. In some applications, the reactants encounter and mix with the heated, high-temperature carrier gas also converging there in the central region, reducing contact with the sidewalls of growth chamber 1 and thus lowering the risk of non-catalytic pyrolysis and carbon deposition on the sidewalls. Meanwhile, the turbulence and shearing effects caused by multi-directional feeding help to fully and uniformly mix the carbon source, catalyst and carrier gas, creating favorable conditions for the uniform nucleation and synchronous growth of carbon nanotubes, and improving product quality and consistency.

[0035] like Figure 5 As shown, this disclosure also proposes a carbon nanotube preparation method, applied to the carbon nanotube preparation apparatus according to an embodiment of the present invention. The central axis of the carrier gas main pipe 21 coincides with the central axis of the growth chamber 1, driving the carrier gas axially into the central region of the growth chamber 1. This ensures that the heat from the carrier gas directly acts on the reaction core region, avoiding heat loss and temperature unevenness caused by flow deviation. Furthermore, at least one pair of reactant pipes 6 are arranged inclined towards the central region of the growth chamber 1 to drive the carbon source and catalyst towards the central region of the growth chamber 1. This allows the carbon source and catalyst to naturally converge into the high-temperature central region where the main carrier gas flow is located, forming a spatial overlap of heat and mass. This improves the mixing efficiency of the reactants and carrier gas while reducing non-catalytic contact with the sidewalls, thereby reducing the risk of carbon deposition. It ensures that the high-temperature carrier gas, carbon source, and catalyst react efficiently in the optimal position, mixing to generate carbon nanotubes under suitable growth conditions, providing reliable hardware support for the continuous production of high-quality carbon nanotubes.

[0036] The method for preparing carbon nanotubes includes the following steps: S100, Carrier gas supply: Carrier gas is introduced into growth chamber 1; S200, reactants: When the carrier gas S100 is introduced, the carbon source and catalyst are introduced into the growth chamber 1 to generate carbon nanotubes. S110, Pretreatment carrier gas: Before introducing carrier gas S100, heat at least a portion of the carrier gas to drive the temperature of the central region of growth chamber 1 to be maintained at a preset temperature after the carrier gas is introduced, so as to match the growth temperature of carbon nanotubes.

[0037] The preset temperature can be one of the following: 600℃, 800℃, 1000℃, 1050℃, 1200℃, 1250℃, 1400℃, etc. It can be understood that the preset temperature can be designed accordingly based on the growth temperature requirements of different carbon nanotubes. The values ​​will not be listed in detail here.

[0038] By pre-treating and heating at least a portion of the carrier gas before it is introduced, and simultaneously introducing a carbon source and catalyst into growth chamber 1 during the introduction of the carrier gas, the heated high-temperature carrier gas becomes the primary heat source for maintaining the temperature of the central region of growth chamber 1, thus matching the growth temperature of carbon nanotubes. This concept fundamentally changes the traditional heat transfer mode that relies on indirect heating from the furnace wall, transforming the carrier gas from a simple transport and dilution medium into an active heat source with efficient heat transport functions. On the one hand, the carrier gas itself carries sufficient heat energy to act directly on the central region of growth chamber 1 through convection, significantly shortening the heat transfer path and reducing thermal resistance, thereby greatly improving heat utilization efficiency and reducing energy consumption. On the other hand, since the heated high-temperature carrier gas is concentrated in the central reaction zone, the reactants also converge with the carrier gas in this region, jointly forming a dynamic thermal field and concentration field centered on the center. This greatly reduces the probability of contact between the reactants and the high-temperature furnace wall, effectively suppressing non-catalytic pyrolysis and carbon deposition, extending the continuous operation time of the equipment, reducing the frequency of downtime for cleaning, and lowering maintenance costs and the risk of production interruption. Meanwhile, using the pre-treated heated carrier gas as the main heat source allows the temperature in the central region of growth chamber 1 to be precisely set and stably maintained within the optimal temperature window for carbon nanotube growth. Optional low-power insulation measures around growth chamber 1 can offset a small amount of heat loss, thereby achieving high-precision and high-stability temperature control. This avoids catalyst deactivation, uneven carbon nanotube nucleation, or structural defects caused by temperature fluctuations or excessive radial temperature differences, ensuring uniform tube diameter, high purity, and good crystallinity of the product. This provides a solid thermal environment guarantee for the large-scale, low-cost, and stable production of carbon nanotubes.

[0039] Specifically, in the carrier gas S100, the carrier gas is introduced linearly and / or swirlingly into the central region of the growth chamber 1, for example, referring to... Figure 3As shown, part of the carrier gas is swirled into the growth chamber 1 through the first carrier gas channel 211, while the other part is linearly introduced into the growth chamber 1 through the second carrier gas channel 220. This combined approach allows the distribution of the high-temperature carrier gas within the chamber to be actively shaped. Linear introduction facilitates the formation of a stable axial heat flow, providing a continuous and uniform thermal background for carbon nanotube growth. Swirled introduction, on the other hand, utilizes the centrifugal and shear effects of the rotating flow to promote thorough radial mixing of the carrier gas, weakening the radial temperature gradient and improving the heat exchange efficiency between the central and peripheral regions. Compared to plug flow high-temperature carrier gas, the residence time of the swirling flow high-temperature carrier gas in the growth chamber 1 is significantly extended, which not only prolongs the heating time but also improves heat utilization. This is because the vortex structure formed by the rotating flow field reduces the axial velocity of the carrier gas, minimizing short-circuiting. Furthermore, the rotating high-temperature carrier gas generates strong shear and centrifugal forces, further optimizing the temperature field uniformity and catalyst and carbon source distribution uniformity within the growth region of the growth chamber 1, promoting a more complete carbon nanotube growth reaction.

[0040] In some applications, in the reactant S200, such as Figure 1 and Figure 2 As shown, carbon source and catalyst are introduced into the central region of growth chamber 1, either separately or in mixture, through at least a pair of reactant pipes 6 uniformly arranged around the circumference of growth chamber 1. This symmetrical and uniformly distributed feeding structure breaks the limitations of traditional single-sided or concentrated feeding, allowing reactants to converge from different directions along similar paths into the central high-temperature carrier gas region. This forms a symmetrical concentration field and thermal field superposition, effectively preventing excessively high local carbon source or catalyst concentrations from causing catalyst poisoning, agglomeration, or excessive carbon nanotube growth. Simultaneously, it promotes rapid mixing of multiple reactant streams in the central region, shortening the time required to achieve uniform mixing and improving the reaction rate and product distribution uniformity. Combined with the linear or cyclonic introduction of the carrier gas, it further integrates the uniform distribution of heat and mass, creating favorable conditions for the preparation of high-purity carbon nanotubes with consistent diameter. Specifically, refer to... Figure 1 Each pair of reactant pipes 6 is arranged at an angle relative to the axis of the growth chamber 1, so that the reactants entering the chamber have certain radial and axial velocity components. Consequently, in the flow of reactant S200, the carbon source, catalyst, and carrier gas converge at the axis of the growth chamber 1, forming a converging flow field. This guides the reactants and carrier gas to efficiently collide and mix in the central region, reducing ineffective retention and side reactions on the sidewalls. It can be understood that the convergence of the carbon source, catalyst, and carrier gas at the axis is equivalent to spatially aligning the heat and mass supply points, maximizing the utilization of the high-temperature carrier gas's thermal energy to directly act on the core catalytic reaction region, avoiding localized low temperatures or insufficient concentrations caused by heat and reactant dispersion. This significantly reduces the radial temperature difference and concentration gradient, improving catalyst utilization and the synchronicity of carbon nanotube growth. Simultaneously, the momentum exchange brought about by the converging flow field helps maintain the dynamic thermal stability of the central region, reducing the interference of temperature fluctuations on the growth process.

[0041] Refer to Figure 1 , Figure 3 and Figure 4 In some embodiments of the present invention, in the pretreatment carrier gas S110, at least a portion of the carrier gas flows along the spiral structure 3 and is heated. On the one hand, this allows the carrier gas to have good temperature uniformity and flow pattern before entering the growth chamber 1, which not only improves the efficiency of pretreatment heating and thermal energy utilization, but also allows it to mix with the reactants more quickly after entering the chamber, reducing local reaction differences caused by uneven carrier gas temperature or flow dead zones, thereby optimizing the overall heat distribution and reaction uniformity in the growth chamber 1 and providing a more controllable thermal environment for carbon nanotube growth. On the other hand, compared with straight channels, which can prolong the contact path and time between the carrier gas and the heating surface, spiral flow heating can improve the sufficiency and uniformity of heating. The beneficial effects can be referred to the specific description in the above embodiments of the carbon nanotube preparation device, which will not be elaborated here.

[0042] Further, the carrier gas spiral heating is extended to allow it to enter the growth chamber 1 spirally. During the carrier gas flow S100, at least a portion of the carrier gas enters the growth chamber 1 in a spiral direction, creating a rotating flow field within the chamber. The centrifugal force generated by the rotation can evenly diffuse and recirculate the carrier gas from the center to the periphery, forming a dynamic circulating thermal convection. For example, in one embodiment, guide vanes (not shown in the figure) can be added to the outlet end 210 of the carrier gas main pipe 21. The guide vanes can convert part of the axial kinetic energy of the high-temperature carrier gas into tangential kinetic energy, thereby significantly improving its rotational characteristics and mixing effect after entering the growth chamber 1. The specific beneficial effects of the spiral entry into the growth chamber 1 can be referred to the specific description in the above-described carbon nanotube preparation device embodiment, which will not be elaborated here. In further applications, during the carrier gas flow S100, the flow rate and / or rotation intensity and / or centrifugal intensity of the carrier gas entering the growth chamber 1 can be adjusted to control the mixing uniformity of the carrier gas, carbon source, and catalyst within the growth chamber 1, and / or control the radial temperature difference of the growth chamber 1. It should be noted that the radial temperature difference and axial temperature of growth chamber 1 are directly related to factors such as the temperature, rotation intensity, or rotation speed of the high-temperature carrier gas. The temperature and flow rate of the rotating high-temperature carrier gas can be quickly and accurately adjusted by external devices, such as the heater 2 and the operating conditions of the flow control valve. This is beneficial to improving the mixing uniformity of the carrier gas, carbon source, and catalyst, as well as the control accuracy of factors such as the radial temperature difference within growth chamber 1. For example, adjusting the flow rate and / or rotation intensity and / or centrifugal intensity of the carrier gas entering growth chamber 1 can coordinate and control the pitch of the spiral structure 3 in the above-mentioned carbon nanotube preparation device embodiment, the intensity and flow rate of the carrier gas introduced into the carrier gas main pipe 21, and the depth of the first carrier gas channel 211 and the second carrier gas channel 220 extending into growth chamber 1, i.e., the depth of the carrier gas main pipe 21 extending into growth chamber 1. This will not be elaborated in detail here. In applications, this multi-parameter adjustable fluid dynamics control strategy allows the process to flexibly optimize the flow field morphology according to different catalyst types, carbon source types, and target carbon nanotube specifications. For example, increasing the rotation intensity can enhance radial mixing and reduce temperature differences, increasing the flow rate can accelerate the overall renewal rate and avoid local saturation, and adjusting the centrifugal intensity can control the carrier gas diffusion range and the size of the central hot zone. This allows for a fine balance between heat distribution and material concentration distribution at the microscopic level, achieving better control of the growth environment. It can not only improve the uniformity of carbon nanotubes but also achieve the optimal match between energy consumption and efficiency for different process requirements, enhancing the versatility and industrial adaptability of the method.

[0043] The following is in conjunction with the appendix Figure 1 and Figure 2This document details one implementation scheme for preparing carbon nanotubes using the aforementioned carbon nanotube preparation apparatus: Nitrogen gas is introduced into the main carrier gas pipe 21 at a flow rate of 500 L / min via the carrier gas auxiliary pipe 5 by adjusting the flow control valve. Simultaneously, the electromagnetic induction coil 4 is activated. The alternating magnetic field generated by the electromagnetic induction coil 4 heats the walls of the main carrier gas pipe 21 and / or the core 22, acting as a heater 2. As the nitrogen gas flows through the spiral structure 3, it is heated by the heater 2 to approximately 1500°C, resulting in a high-temperature carrier gas. This high-temperature carrier gas is introduced into the growth chamber 1 axially and directed towards its radial center region. Furthermore, the mixing uniformity of the carrier gas, carbon source, and catalyst within the growth chamber 1, as well as the radial temperature difference of the growth chamber 1, is controlled by adjusting the rotation intensity of the carrier gas to meet the process conditions. The continuous supply of high-temperature carrier gas maintains the temperature in the radial center region of the growth chamber 1 at approximately 1250°C. A low-power heat preservation heating device is then activated to maintain the temperature around the growth chamber 1. A mixed solution of ferrocene, thiophene, and ethanol, with ferrocene and thiophene contents of 2.5 wt% and 1 wt%, is heated and vaporized into a vaporization reactant. This reactant is then uniformly mixed with hydrogen and nitrogen in a volume ratio of 1:1:2 and introduced into the radial center region of growth chamber 1 through reactant pipe 6. The high-temperature carrier gas is then fully mixed with the carbon source and catalyst in the radial center region of growth chamber 1 to generate carbon nanotubes. The generated carbon nanotubes are then carried by the carrier gas into the receiving chamber for gas-solid separation. Compared to the traditional "external heating wall" method, carbon buildup on the inner wall of the chamber is significantly reduced.

[0044] Other components and operations of the carbon nanotube preparation method according to the embodiments of this disclosure are known to those skilled in the art and will not be described in detail here.

[0045] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing carbon nanotubes, characterized in that, Includes the following steps: Carrier gas is introduced into the growth chamber; Reactant flow: During carrier gas flow, carbon source and catalyst are introduced into the growth chamber to generate carbon nanotubes; Pretreatment of carrier gas: Before the carrier gas is introduced, at least a portion of the carrier gas is heated to drive the temperature of the central region of the growth chamber to remain at a preset temperature after the carrier gas is introduced, in order to match the growth temperature of carbon nanotubes.

2. The method for preparing carbon nanotubes according to claim 1, characterized in that: In the carrier gas process, the carrier gas is introduced linearly and / or swirlingly into the central region of the growth chamber.

3. The method for preparing carbon nanotubes according to claim 2, characterized in that: In the reaction mixture, the carbon source and the catalyst are introduced into the central region of the growth chamber, either separately or in mixture, through at least a pair of reaction pipes uniformly arranged around the periphery of the growth chamber.

4. The method for preparing carbon nanotubes according to claim 3, characterized in that: Both reactant conduits are arranged at an angle relative to the axis of the growth chamber; during the reaction, the carbon source, the catalyst, and the carrier gas all converge at the axis of the growth chamber.

5. The method for preparing carbon nanotubes according to claim 2, characterized in that: In the pretreatment carrier gas, at least a portion of the carrier gas flows along a spiral structure and is heated.

6. The method for preparing carbon nanotubes according to claim 5, characterized in that: At least a portion of the wall of the spiral structure is configured as an electromagnetic induction element, which generates an alternating magnetic field through an electromagnetic induction coil, causing the electromagnetic induction element to heat up and heat the carrier gas flowing through the spiral structure.

7. The method for preparing carbon nanotubes according to any one of claims 1 to 6, characterized in that: During the carrier gas process, at least a portion of the carrier gas swirls into the growth chamber.

8. The method for preparing carbon nanotubes according to claim 7, characterized in that: In the process of introducing carrier gas, the flow rate and / or rotation intensity and / or centrifugal intensity of the carrier gas entering the growth chamber are adjusted to control the mixing uniformity of the carrier gas, the carbon source and the catalyst in the growth chamber, and / or control the radial temperature difference of the growth chamber.

9. A carbon nanotube preparation apparatus, characterized in that: The carbon nanotube preparation apparatus for performing the carbon nanotube preparation method according to any one of claims 1 to 8 includes: Growth chamber; A heater capable of heating the carrier gas, the heater including a carrier gas main pipe, the central axis of the carrier gas main pipe coinciding with the central axis of the growth chamber, so as to drive the carrier gas axially into the central region of the growth chamber; At least one pair of reactant channels are uniformly arranged around the outer periphery of the main carrier gas channel. The reactant channels are inclined toward the central region of the growth chamber to drive the carbon source and catalyst to the central region of the growth chamber and mix with the carrier gas to generate carbon nanotubes.

10. The carbon nanotube preparation apparatus according to claim 9, characterized in that: The heater further includes a core and an electromagnetic induction coil. The core is arranged in the main gas pipe and forms a first gas channel with the main gas pipe. The first gas channel is connected to the growth chamber and inputs the gas. At least a portion of the inner wall of the main gas pipe and / or at least a portion of the outer wall of the core has a helical surface to form a helical structure in at least a portion of the first gas channel. At least a portion of the wall of the helical structure is an electromagnetic induction element. The electromagnetic induction coil is energized to generate an alternating magnetic field and drive the electromagnetic induction element to heat up, thereby heating the gas flowing through the helical structure. A second gas channel is provided in the middle of the core. The second gas channel extends along the side facing the growth chamber and is connected to the growth chamber to input a portion of the gas. The first carrier gas channel is further provided with a spiral structure at one end that is connected to the growth chamber, so as to drive the carrier gas to swirl into the growth chamber; and / or, the pitch of the spiral structure gradually decreases along the side facing the growth chamber.

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